The Effect of Capsular Repair Location on Humeral Head Position and Translation After Distal Tibial Allograft Reconstruction: A Cadaveric Study

Background: Distal tibial allograft (DTA) reconstruction has emerged as an effective option for the treatment of recurrent shoulder instability with glenoid bone loss (GBL). However, the ideal location for capsular repair during the procedure remains undetermined. Purpose: To evaluate the effect of capsular repair location on humeral head positioning and anterior translation after DTA. Study Design: Controlled laboratory study. Methods: Nine human cadaveric specimens (mean age, 62.2 years [range, 52-69 years]) underwent biomechanical testing in a simulated bone loss model. The rotator cuff tendons were loaded, and anterior stability testing was performed using a Kuka robot with the shoulder in 90° of abduction and neutral external rotation. A motion capture system recorded humeral head position and anterior translation. GBL (mean, 32%) was created, and a DTA graft was prepared to restore 100% of the native glenoid width. The following conditions were tested: intact, soft tissue Bankart lesion, DTA without capsular repair (DTA), DTA with capsule repaired to the graft (intra-articular), and DTA with capsule repaired to the glenoid (extra-articular). A repeated measures analysis of variance was performed to compare the translation and humeral head resting position between the five capsulolabral conditions. Results: There was no difference in anterior translation when comparing DTA without capsular repair and the DTA with the capsule repaired to the graft (5.1 vs 5.3 mm; P > .999), and there was no difference in anterior translation between either of these conditions and the intact state ( P > .999 for both). However, capsular repair to the glenoid demonstrated a significantly decreased anterior translation (0.7 vs 7 mm; P < .001) as well as a statistically significant posterior shift in the resting position (–2.5 vs 1.8 mm; P = .004) when compared with the intact state. Conclusion: When performing a DTA reconstruction for large GBL, capsular repair to the native glenoid results in a more posterior resting humeral head position and less maximum anterior translation of the humeral head during time-zero biomechanical testing in cadaveric specimens. DTA without capsular repair and DTA with capsular repair to the graft restore glenohumeral position and motion closer to the native state. Clinical Relevance: Capsular repair to the native glenoid may overconstrain the glenohumeral joint when performing distal tibial allograft reconstruction in the setting of large glenoid bone loss, but further study is required to determine the impact on patient-reported outcomes or long-term arthritis risk.